Hardware-In-Loop Testing for Dishwasher Control Board

This repository contains an automated Hardware-In-Loop (HIL) testing framework for validating dishwasher control electronics. Tests run on a Raspberry Pi 5 connected to the Device Under Test (DUT) via GPIO and I2C, simulating real-world inputs and verifying correct outputs.

Overview

The test harness:

• Simulates inputs to the control board (door switch, water level, temperature sensor, manual switches)
• Monitors outputs from the control board (motor contactor, heater, valves, pumps, indicator lights)
• Validates behavior matches expected state machine transitions

Tests execute in a GitHub Actions CI/CD pipeline using the systemd runner on the Pi 5.

Architecture

• Output relay board: https://czh-labs.com/products/din-rail-mount-8-spdt-iot-power-relay-module-for-raspberry-pi (or similar 8-ch relay board)

• I2C DAC: https://www.amazon.com/dp/B0BWTX88JL

• Custom input board: https://github.com/jimpudar/hil-input-board-kicad

• Dishwasher control board: https://github.com/jimpudar/dishwasher-controller-kicad

• Dishwasher control software: https://github.com/jimpudar/dishwasher-controller-qpn

┌─────────────────────┐         ┌─────────────────────┐
│   Raspberry Pi 5    │         │   DUT (Dishwasher   │
│   (Test Harness)    │         │   Controller)       │
│                     │         │                     │
│  Output Relays──────┼────────>│  Inputs             │
│  (Simulated inputs) │         │                     │
│                     │         │                     │
│  Input Board <──────┼─────────│  Outputs            │
│  (Monitored outputs)│         │                     │
│                     │         │                     │
│  I2C (MCP4725) ─────┼────────>│  RTD Temperature    │
│  (Temp simulation)  │         │  Sensor Input       │
└─────────────────────┘         └─────────────────────┘

Physical Connections

Harness to DUT Wiring

Output Pins (Raspberry Pi → DUT)

These pins simulate inputs to the dishwasher control board.

These are connected to the DUT through the relay board.

GPIO	Signal	Harness Connection	DUT Connection
5	E-Stop	Relay 1 NO / Common	ESTOP+ / ESTOP- QC Terminals
6	Manual Rinse	Relay 2 NO / Common	MAN SW 3 / MAN SW 2 QC Terminals
13	Manual Wash	Relay 3 NO / Common	MAN SW 1 / MAN SW 2 QC Terminals
16	Door Switch	Relay 4 NO / Common	DOOR+ / DOOR- QC Terminals
19	Timed Fill	Relay 5 NO / Common	FILL SW 3 / FILL SW 2 QC Terminals
20	Stop	Relay 6 NO / Common	FILL SW 1 / FILL SW 2 QC Terminals
21	Float	Relay 7 NO / Common	FLOAT+ / FLOAT- QC Terminals
26	TCO	Relay 8 NO / Common	TCO+ / TCO- QC Terminals

Input Pins (DUT → Raspberry Pi)

These pins monitor outputs from the dishwasher control board.

The custom input board is used. The input board needs to be configured as follows:

CH1, CH2: Active HIGH, isolated low sides

CH3-CH8: Active LOW, all low sides connected to DUT chassis

GPIO	Signal	DUT Connection	Description
4	Motor Contactor	+ to MOTOR+, - to MOTOR-	Sense the voltage drop across the contactor coil.
12	Heater Contactor	+ to HEATER+, - to HEATER-	Sense the voltage drop across the contactor coil.
17	Rinse Valve Relay	+ to TP28	Sense the arduino output
22	Detergent Pump Relay	+ to TP26	Sense the arduino output
23	Rinse Aid Pump Relay	+ to TP24	Sense the arduino output
24	Timed Fill Indicator	+ to TP20	Sense the arduino output
25	Rinse Indicator	+ to TP13	Sense the arduino output
27	Ready Indicator	+ to TP9	Sense the arduino output

I2C Connection

The MCP4725 DAC simulates the RTD temperature sensor input to the control board.

The GND pin connects to the DUT chassis, and the OUT pin connects to TP25.

Power and Ground

240VAC is supplied using a homemade dim-bulb / isolation transformer. This powers the entire DUT.

There is NO chassis ground connection while connected to the isolation transformer.

Care must be taken to not touch any of the 120VAC terminals on the DUT board, as they can be live during testing.

The Raspberry Pi 5 is powered using the PoE+ Hat, which supplies the relays through the 5V rail.

The DUT is not galvanically isolated from the Pi because of the DAC connection. If an external 4-20mA current source is used instead of the DAC, fewer tests can be run but the Pi is galvanically isolated.

Hardware Setup

Raspberry Pi Preparation

This project uses a Raspberry Pi 5, configured to run headless.

1. Use Raspberry Pi Imager to write Raspberry Pi OS Lite (64-bit) to the SD card.

2. Enable SSH access and ensure your public key is present or password is configured properly.

3. Merge the cloud-init configuration from this repository:

   dotnet run cloud-init/merge.cs <user-data on SD card> cloud-init/user-data-partial.yml

4. Eject the SD card, insert it into the Pi, and boot. It will become available via SSH after cloud-init completes.

5. SSH into the Pi and run the script in the home directory to register the worker with GitHub Actions.

TODO: Currently I have been having failures with the cloud-init on first boot because NTP sync is happening out of order. If this happens, you can SSH to the Pi, run cloud-init clean, and reboot. It should succeed on the second try since the clock will have been set properly.

TODO: I believe you currently need to manually enable I2C using the raspi-config TUI. This should be added to cloud-init.

Running Tests

CI/CD

Tests can be run manually via GitHub Actions on a self-hosted runner tagged [self-hosted, hil].